Safety stop for searchlights



Dec. 4', 1928 1,694,039

M. L. PATTERSON SAFETY STOP FOR SEARCHLIGHI'S Filed April 24, 1922 A C Q Suoentoz Patented Dec. 4, 1928.

UNITED STATES PATENT OFFICE.

man'rm L. "ra'rraasom or BOGOI'A, NEW aanserf assmnoa TO THE SPERRY emscora comramr, or BROOKLYN, NEW YORK, A CORPORATION QFVNEW YORK.

SAFETY STOP FOB SEARCKLIGHTS.

' Applicatton'filed April 24, 1922. Serial No. 558,848.

vating motor, striking against the stops was.

sufiicicnt to cause strains on the gears. shafting, pins and other parts of'the searchlight, and to cause possible damage to the'motor due to the excess current. It is an object of this invention, therefore, to providemeans for braking the movement of the lamp as it approaches the stopsin elevating or depressing. This is accomplished without opening the motor circuit, otherwise it would be impossible to reverse the movement of the lamp to move it away from the stops. The present invention therefore provides in the closed circuit of theelevating motor means for reducing the speed of the motor as the lamp approaches the stops which limit the elevation or dcpresson. For this purpose there is provided in the circuit of the elevatin motor a limit switch so designed that, when opened, the motor circuit includes a fixed resistance which cuts down the speed and power of the motor. When said switch is closed, the resistance isshort-circuited so that the elevating motor is connected directly to the line. Means are provided whereby said switch may be opened at any predetermined maximum elevation or depression.v

It is not unusual to; provide sto s for limiting, the movement of the Searchlight in azimuth, the light being free to make complete rotations in either direction. Where,

owever, limiting stopsare provided to limit the movement in azimuth, it will be understood that the same inventionhereinafter described in connection with the elevating motor can be applied in connection with the azimuth motor. 1'

Other objects and advantages will hereinafter appear. 7 5

The accompanying drawing illustrates mainly in diagrammaticv form, an embodiment of my invention.

The invention is applied to a searchlight having an azunuth motor A and an elevat-- mg motor E, as disclosed 1n the application of Theodore Hall, Serial No. 319,383, filed August 23rd,'1919, Pat. No. 1,537,770, May 12, 1925. Each of said motors has a field 10 and 11, respectively, energized from the main current leads 12 and 13 by lead-lines 14. 15 and 16, 17 respectively. The armature 18 of the azimuth motor is connected by leads 20 and 21 to an azimuth controller AC, while armature 19 of the elevating motor is connected by leads 22 and 23 to an elevating controller EC. The azimuth motor is generally mounted on a fixed base since it rotates the entire lamp, and the leads may,

therefore be connected directly thereto, but the elevating motor moves with the main frame of the searchlight and it is therefore necessary to provide slip-rings 30 and 31 for conducting the current thereto.

For controlling the speed of either motor, both of said controllers are wired to a potentiometer P. Each controller comprises two sets of contacts here shown as 1 to 8 inelusive and contacts C similarl Y arranged on opposite sides of an arc, li e contacts being joined together. A double contact member comprising two arms 35 and 36 in fixed relation to each other cooperates with said contacts, each arm cooperating with a set of contacts on one side of the are. It will be apparent that as the contact member is rotated in one direction or the other, one arm will move upwardly on one set of contacts and downwardly on the other set. In its central position both arms of thecontact member engage contacts C, and hence the circuit of the armature lies through lead 20 across contacts C to lead 21, thus excludin the potentiometerentirely from its circurt. Since there is no drop in potential in the armature circuit in this position of the contact arms, the motor is at rest. When, however, the contact member is rotated through one contact space, for example, contact arm 35 engages contact 4 and contact arm 36.engages contact 5, the circuit is then through lead 20 to contact 5, lead 45 to contact 5 of potentiometer P. through the potentiometer to contact 4, lead 44 to contact 4 of the controller, and lead 21 to the armature. There is thus included the drop in potential included between contacts 4 and 5 of the potentiometer, said drop being a fraction of the total drop between contacts 1 and 8 of the ot'entiometer which corresponds to the position of the contact member where one arm engages contact 1 of T e controllers AC and EC for the azimuth and elevating motors, respectively,

are similar, and by connecting the contacts of both controllers to the same junctions $1 to 48' inclusive, the same leads 41 to 48 melusive and the same potentiometer P may be utilized in connection with both controllers. It will be obvious that both con trollers may be 0 erated simultaneously.

Scales are usua ly provided to enablethe operator to read the number of degrees of turn in azimuth and in elevation, and lights 50, here shown as connected to the main line, may be providedadjacent said scales to facilitate reading thereof.

The controllers AC and EC, junction-box J, in which are located the junctions 41' to 48 inclusive and the junctions of leads 20, 21, 22 and 23, are preferably located at a distance from the lam and its control motors, and a coupling K is preferably interposed to enable the plurality of connecting leads to be readily connected to or dis connected from the lamp. i

As hereinbefore pointed out, there are usually provided stops on the supportin frame and shown diagrammatically at which limit the elevation and depression of the lamp b :engaging lugs, indicated diagrammatica ly at L, on the drum, and it is apparent that motor E, rotating the lamp, willeause the latter to strike the sto s while it is travelin at full speed, since t e operator stationed at a distance does not'know when the lamp is approaching the sto s. It is not desirable to interpose a circuitbreaker to be operated by the lamp before reaehin the stops, since it would then be impossi le to o erate the lamp in the reverse direction, wit out actuation ofhandswitches since the circuit is open. This invention therefore introduces a braking element at the roper time, without opening the circuit through the motor. The circuit through the armature of motor E from slip-rings 31 ordinarily extends through lead 52 (which is a continuation of conduit 22), limit switch L, conduit 51, and conduit 53 (which is a continuation of conduit 23).' When the lamp approaches its limiting stops, means are provided for breakin the circuit through switch L, and the circuit I then extends from slip-rings31 through resistance R (connected in series in the circuit) and lead 53. The introduction of this resistance in the circuit slows down the motor to such an extent as to prevent damage'which might otherwise be caused-by the striking of the lamp against the stops.

Ordinarily therefore the circuit is shunted across resistance R so that substantially all of the current flows through the'shunt.

For operating the limit switch when the lamp approaches a limiting sto the frame 55 of the lamp which swings a out a horizontal axis during elevation or d pression ofthe li ht is provided with a c m 60 so positione shortly before the lamp engages the stops, as to contact with a movable bar 61, which carries leaf spring contacts 62 normally in engagement with contacts 63 to depress said bar against the action of a spring 64 and break the circuit through leads 52 and 51 to the armature 19.; The c1r-' cuit through said armature now includes resistance R, and this circuit will be maintained as long as cam '60 engages bar 61. At any time, however, the lam may be moved in the opposite direction by rotating the contact arms 35, 36 in the desired direction. Just before the lamp reaches its opposite limit stop, a second cam 68 may be provided to engage and depress bar 61. By providing a pin and slot connection 69, 70 between each cam and the frame 55 of the lam the point at which the motor is slowed own can be varied at will in accordance with the particular conditions.

In accordance with .the provisions of the patent statutes, I have herein described the principle of operation ofm invention,

together with the apparatus, w ich I now consider to represent the.best embodiment thereof, but I desire to have it understood that the apparatus shown isonly illustrative and that the invention can be carried out by other means. Also, while it is designed to use the various features and'elements in the combination and relations described, some of these may be "altered and others omitted without interferin with the more general results outlined, an the invention extends to such use.

Having herein described my invention what I claim and desire to secure by- Letters Patent is,

1. In combination with a movable device, electric means for movin said device, said means including a contro er and an electric motor, a circuit for transmitting a relatively merely large current to said motor and a second eirrent to said motor, means for limiting the movement of said device, means normally rendering one of said circuits effective, means for rendering ineffective the normally effective circuit and rendering the other of said circuits effective, as the device approaches said limiting means, to vary the speed of the device, and means permitting means including a controller and an electric motor, a circuit for transmitting a relatively large current to said motor and a second circuit for transmitting a relatively small current to said motor, means for limiting the movement of said device, means normally rendering said first circuit effective, means for rendering said first circuit ineffective and said second circuit efi'ective, as the device approaches said limiting means, for reducing the speed of the device, and means permitting .said first means to reverse the direction of MARTIN L. PATTERSON.

sign ature. 

